Toll-like receptors (TLRs) recognize microbial components and initiate inflammation during infection. TLR2 is the receptor for microbial lipoproteins and other parts of Gram-positive and Gram-negative bacteria, and fungi. The endothelium expresses TLR2 and is important in sepsis-induced organ failure. We found that activation of TLR2 broadly affects endothelial cell (EC) functions, leading to upregulation of cytokine and chemokine production, increased neutrophil trafficking, altered expression of coagulation pathway intermediaries, and increased permeability. We probed the signaling pathways involved in TLR2-dependent activation of the EC by treating human umbilical vein EC (HUVECs) with lipopeptide TLR2 agonists and performed immunoblots, NF-κB EMSA’s, transcription factor arrays, and qRT PCR to assess responses. We found that TLR2 agonists transiently activate p38-MAPK and JNK at early time points and induce a sustained, albeit weak, activation of the transcription factor NF-κB. Through the use of siRNA knockdown and specific inhibitors, we determined that p38-MAPK, JNK, and NF-κB are necessary for TLR2-dependent upregulation of IL-6, IL-8 and TLR2 itself. Additionally, using mRNA human immune arrays, we found that markers of neutrophil trafficking and activation are most robustly upregulated by TLR2-dependent activation of the endothelium. We are currently investigating the mechanisms responsible for neutrophil trafficking and activation responses in more detail.
- Copyright © 2011 by The American Association of Immunologists, Inc.